unusual slow calculation with larger systems
Posted: Tue Jun 04, 2013 10:36 pm
Hi, All,
We tried to compile the vasp 5.2 and 5.3 on new linux cluster (http://www.rcac.purdue.edu/userinfo/resources/carter/). It worked quite well at the beginning. But after we increase the system size (e.g. from non-spin polirized MgO to spin polirized and +U corrected FeO; from small vacuum to large vacuum). The calculation became extremely slow in some cases. In such slow cases, OUTCAR file showed that the "EDDIAG:" and "ORTHCH:" time is much longer (hundreds seconds and even > 1000s) than it in the normal case (< 10s). The "RMM-DIIS:" time do not have a big different in all the cases.
We checked the memory usage and intra-nodes communications and it turned out no limitations from the hardware.
Could anyone give us some hint on how to solve this problem?
Thank you in advance!
zhao
We tried to compile the vasp 5.2 and 5.3 on new linux cluster (http://www.rcac.purdue.edu/userinfo/resources/carter/). It worked quite well at the beginning. But after we increase the system size (e.g. from non-spin polirized MgO to spin polirized and +U corrected FeO; from small vacuum to large vacuum). The calculation became extremely slow in some cases. In such slow cases, OUTCAR file showed that the "EDDIAG:" and "ORTHCH:" time is much longer (hundreds seconds and even > 1000s) than it in the normal case (< 10s). The "RMM-DIIS:" time do not have a big different in all the cases.
We checked the memory usage and intra-nodes communications and it turned out no limitations from the hardware.
Could anyone give us some hint on how to solve this problem?
Thank you in advance!
zhao